Southern Root-knot Nematode (Meloidogyne incognita) Map

The southern root-knot nematode (Meloidogyne incognita) can infect a wide variety of host plants across the United States. This map summarizes the distribution of M. incognita in the field crops (agronomic and vegetable crops) and excludes home gardens, high tunnels, greenhouses, and nurseries where it would be artificially protected from winter temperatures. A highlighted county indicates that the southern root-knot nematode was confirmed in at least one field, therefore implementing a practice to manage the southern root-knot nematode is on a field-by-field basis. 

Of the field crops grown in the southern US, this nematode species is often ranked in the top five most important diseases in cotton and soybean. Spindle-shaped galls can be observed on infected cotton and soybean roots, which is one method to determine if root-knot nematodes are present. Another method is to collect soil samples and submit them to a nematode diagnostic lab for processing. A soil sample is the only method to determine the population density of root-knot nematodes present. 

Yield losses vary based on cultivar susceptibility, nematode population density, and soil texture. To mitigate yield losses, management tactics that reduce nematode population densities or protect the developing seedling root system are used. Crop rotation sequences with a non-host crop such as peanut can reduce nematode densities. Host plant resistance is available in cotton and soybean and can reduce nematode densities and increase lint/grain yield when used in fields where the nematode is present. Nematicides should be paired with host plant resistance for season long protection. For more detailed information on managing the southern root-knot nematode see the “An Overview of Root-Knot Nematodes” publication (CPN-1027).